Switch from com.io7m.xom:xom:1.2.10 to xom:xom:1.3.7.

com.io7m.xom:xom hadn't been updated since Oct 2013, whereas xom:xom was
last updated in Mar, 2021. All tests still pass. We hadn't tried this
earlier because https://mvnrepository.com/artifact/xom/xom had a
prominent note that said
        'This artifact was moved to: com.io7m.xom » xom'
but based on  https://xom.nu/history.html, it became obvious that they
were still doing active development. We will monitor this however as the
WAF tests (which is the only ESAPI component that uses xom) are not very
thorough so something could slip through.

Author: kwwall

pom.xml

@@ -169,9 +169,9 @@
             </exclusions>
         </dependency>
         <dependency>
-            <groupId>com.io7m.xom</groupId>
+            <groupId>xom</groupId>
             <artifactId>xom</artifactId>
-            <version>1.2.10</version>
+            <version>1.3.7</version>
             <exclusions>
                 <!-- excluded because we directly import newer versions. -->
                 <exclusion>